1. Field
Example embodiments relate to semiconductor devices having reduced dislocation densities and/or tensile stresses. Example embodiments also relate to methods of manufacturing semiconductor devices.
2. Description of the Related Art
Conventional nitride-based semiconductor devices use a sapphire substrate. However, sapphire substrates are relatively expensive and relatively difficult to process. Sapphire substrates also have relatively low electric conductivity. Furthermore, sapphire substrates are relatively difficult to manufacture in relatively large sizes because warping may occur during relatively high temperature processes (e.g., during epitaxial growth) due to the relatively low thermal conductivity.
Other conventional nitride-based semiconductor devices use a silicon (Si) substrate instead of a sapphire substrate. Because silicon substrates have a higher thermal conductivity than sapphire substrates, silicon substrates are not warped significantly at relatively high temperatures while growing a nitride thin film. Accordingly, it is possible to grow a relatively large thin film on a silicon substrate. However, when a nitride thin film is grown on a silicon substrate, a dislocation density may increase due to a mismatch in lattice constants between the silicon substrate and the nitride thin film. Cracks may also form more easily due to the thermal expansion coefficient mismatch between the silicon substrate and the nitride thin film.
It is relatively difficult to obtain both relatively low dislocation density and relatively low crack formation using conventional methods because reducing dislocation density causes residual tensile stress, which causes cracks to form. Moreover, when crack formation is reduced, a dislocation density generally increases using conventional methods. Therefore, reducing both dislocation density and crack formation is relatively difficult when growing a nitride thin film on a silicon substrate.